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Article
Publication date: 8 April 2020

Mohammad Saeid Aghighi, Christel Metivier and Hamed Masoumi

The purpose of this paper is to analyze the natural convection of a yield stress fluid in a square enclosure with differentially heated side walls. In particular, the Casson model…

Abstract

Purpose

The purpose of this paper is to analyze the natural convection of a yield stress fluid in a square enclosure with differentially heated side walls. In particular, the Casson model is considered which is a commonly used model.

Design/methodology/approach

The coupled conservation equations of mass, momentum and energy related to the two-dimensional steady-state natural convection within square enclosures are solved numerically by using the Galerkin's weighted residual finite element method with quadrilateral, eight nodes elements.

Findings

Results highlight a small degree of the shear-thinning in the Casson fluids. It is shown that the yield stress has a stabilizing effect since the convection can stop for yield stress fluids while this is not the case for Newtonian fluids. The heat transfer rate, velocity and Yc obtained with the Casson model have the smallest values compared to other viscoplastic models. Results highlight a weak dependence of Yc with the Rayleigh number:YcRa0.07. A supercritical bifurcation at the transition between the convective and the conductive regimes is found.

Originality/value

The originality of the present study concerns the comprehensive and detailed solutions of the natural convection of Casson fluids in square enclosures with differentially heated side walls. It is shown that there exists a major difference between the cases of Casson and Bingham models, and hence using the Bingham model for analyzing the viscoplastic behavior of the fluids which follow the Casson model (such as blood) may not be accurate. Finally, a correlation is proposed for the mean Nusselt number Nu¯.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 5
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 22 July 2019

Behnam Rafiei, Hamed Masoumi, Mohammad Saeid Aghighi and Amine Ammar

The purpose of this paper is to analyze the effects of complex boundary conditions on natural convection of a yield stress fluid in a square enclosure heated from below (uniformly…

Abstract

Purpose

The purpose of this paper is to analyze the effects of complex boundary conditions on natural convection of a yield stress fluid in a square enclosure heated from below (uniformly and non-uniformly) and symmetrically cooled from the sides.

Design/methodology/approach

The governing equations are solved numerically subject to continuous and discontinuous Dirichlet boundary conditions by Galerkin’s weighted residuals scheme of finite element method and using a non-uniform unstructured triangular grid.

Findings

Results show that the overall heat transfer from the heated wall decreases in the case of non-uniform heating for both Newtonian and yield stress fluids. It is found that the effect of yield stress on heat transfer is almost similar in both uniform and non-uniform heating cases. The yield stress has a stabilizing effect, reducing the convection intensity in both cases. Above a certain value of yield number Y, heat transfer is only due to conduction. It is found that a transition of different modes of stability may occur as Rayleigh number changes; this fact gives rise to a discontinuity in the variation of critical yield number.

Originality/value

Besides the new numerical method based on the finite element and using a non-uniform unstructured grid for analyzing natural convection of viscoplastic materials with complex boundary conditions, the originality of the present work concerns the treatment of the yield stress fluids under the influence of complex boundary conditions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Open Access
Article
Publication date: 12 June 2024

Inka Malinen, Timo Jama, Antti Tanninen and Hilla Nordquist

The aim of this study was to identify the perceived competence of Finnish paramedics to operate in different chemical, biological, radiological, nuclear, and explosive (CBRNE…

Abstract

Purpose

The aim of this study was to identify the perceived competence of Finnish paramedics to operate in different chemical, biological, radiological, nuclear, and explosive (CBRNE) incidents.

Design/methodology/approach

This was a descriptive cross-sectional survey study. The material was collected using a previously developed questionnaire, which was modified in accordance with the study aim. The target group was paramedics of the Päijät-Häme region of Finland (N = 166), whose role entailed active operational duties during the survey. Descriptive statistical methods were used.

Findings

Paramedics reported low levels of training related to CBRNE incidents, and most felt that more training was needed. Chemical and explosive-related incidents were regarded as more likely to occur than others. Additionally, paramedics with more work experience perceived themselves as having higher competence only in chemical and explosive-related incidents. Overall, paramedics perceived their CBRNE competence as low.

Originality/value

The perceived CBRNE competence of paramedics has not been studied sufficiently. Paramedics felt chemical and explosive related incidents were more likely to occur than others, and competence related to those two was also better perceived. This study showed that paramedics could benefit from more training to respond to CBRNE incidents to improve perceptions of their competence. However, the desired competence, actual competence, and appropriate training to respond to CBRNE incidents require further research.

Details

International Journal of Emergency Services, vol. 13 no. 2
Type: Research Article
ISSN: 2047-0894

Keywords

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